The invention relates to a combustion chamber arrangement with a combustion chamber in which a burner is arranged. The combustion chamber is especially an annular combustion chamber of a gas turbine.
DE 195 41 303 A1 discloses a combustion chamber arrangement of a gas turbine into which a number of burners open. The gas turbine has a turbine shaft with a main axis. Each burner is directed along a main axis. To achieve particularly high efficiency, the main axis of each burner is tilted with respect to the main axis of the turbine shaft for producing a swirl of a working medium. Such a tilting of the burners dispenses with the need for a swirl-producing structural part.
In DE 43 39 094 A1 there is a description of a method of damping thermoacoustic oscillations in the combustion chamber of a gas turbine. In the combustion of fuels in the combustion chamber of an industrial gas turbine, an aircraft engine or the like, the combustion processes can cause instabilities or pressure fluctuations which, under unfavorable conditions, induce thermoacoustic oscillations, which are also referred to as combustion oscillations. These not only represent an undesired source of noise, they also lead to inadmissibly high mechanical loads on the combustion chamber. Such a thermoacoustic oscillation is actively damped by the location of the fluctuation in heat release associated with the combustion being controlled by injecting a fluid.
U.S. Pat. No. 4,967,562 discloses a turbine engine in which particularly good fuel distribution in the combustion air is achieved. This is realized by fuel being injected from a nozzle onto a baffle plate. As this happens, the fuel is finely atomized and is well distributed in the combustion air which is flowing past the baffle plate.
DE 196 15 910 A1 discloses a burner arrangement, especially for a gas turbine. At least two groups of burners are provided, in each case comprising at least one burner of the same size and geometry for fitting out a combustion chamber. At least one group of burners represents the main burners. The other group of burners is designed as a group of disturbing burners, each of the disturbing burners being inclined with respect to a main burner such that a flame disk formed by the main burner is disturbed in its homogeneity and symmetry. In this way, pressure pulsations can be avoided.
The object of the invention is to specify a combustion chamber arrangement which has favorable characteristics, especially with regard to the avoidance of thermoacoustic oscillations.
This object is achieved according to the invention by a combustion chamber arrangement with a combustion chamber which has a combustion chamber axis and in which there is arranged a burner which has an opening for a combustion gas stream to flow into the combustion chamber along an opening direction, a deflecting means being arranged in the region of the opening for deflecting the combustion gas stream into an inflow direction which differs from the opening direction and the inflow direction being defined as a unit vector, with a reference point in the opening and a unit length, by three component vectors:
a) an axial component, which is parallel to the combustion chamber axis,
b) a planar component, which is perpendicular to the combustion chamber axis and lies in a connecting plane which is defined by the reference point and the combustion chamber axis,
c) an orthogonal component, which is perpendicular to the combustion chamber axis and to the planar component.
In such a combustion chamber arrangement, the location of the combustion of the combustion gas flowing out of the burner is shifted by the deflection of the combustion gas stream with the aid of the deflecting means. Such shifting has the consequence that the distances between the location of the combustion and the combustion chamber wall change. As a result, the acoustic system which is formed by the burner and combustion chamber is acoustically detuned. By suitable alignment of the deflecting means, i.e. by suitable selection of the deflecting direction, the formation of a thermoacoustic oscillation can consequently be suppressed.
The combustion chamber is preferably rotationally symmetrical about the combustion chamber axis.
The orthogonal component preferably has a length different from zero. An orthogonal component of the inflow direction different from zero means that the direction of the inflowing combustion gas stream does not lie in the connecting plane, i.e. the inflow direction is turned with respect to the combustion chamber axis. Such oblique flowing in makes shifting of the location of the combustion possible in a particularly efficient way, so that formation of a thermoacoustic oscillation is suppressed.
A further burner is preferably provided, which further burner has an opening for a combustion gas stream to flow into the combustion chamber along a further inflow direction, which further inflow direction is defined as a unit vector, with a further reference point in the opening of the further burner and with the unit length, by three further component vectors:
a) a further axial component, which is parallel to the combustion chamber axis,
b) a further planar component, which is perpendicular to the combustion chamber axis and lies in a further connecting plane, which is defined by the further reference point and the combustion chamber axis,
c) a further orthogonal component, which is perpendicular to the combustion chamber axis and to the further planar component.
The axial component preferably has a length different from the further axial component. The different lengths of the axial components of the two burners have the consequence that the respective inflow directions of the two burners are inclined or tilted differently with respect to the combustion chamber axis. Such a different inclination of the inflow direction has the effect that the locations of the respective combustion can be set in relation to one another such that combustion oscillations emanating from these locations disturb or even eliminate one another. In particular, such an arrangement can be used for a combustion chamber with a multiplicity of burners. In this case it is possible for only two burners or else more than two burners to be tilted differently with respect to the combustion chamber axis. Depending on the geometrical design of the combustion chamber, it is also advantageous to tilt most of the burners or all the burners differently with respect to the combustion chamber axis.
Tilting of a burner or plurality of burners with respect to the combustion chamber axis, manifested by a different length of the axial component of the burners, may also be combined with turning. Such turning corresponds to an orthogonal component different from zero as already referred to above The possibility of simultaneous turning and tilting provides a wide range of possible selections for the shifting of the location of the combustion. This results in a multiplicity of configurations, from which it is possible to select one which ensures acoustic detuning of the acoustic system comprising the combustion chamber and burner, i.e. with which particularly great suppression of thermoacoustic oscillations is achieved. Such a selection may be made, for example, by trying out various configurations and selecting the one with the best thermoacoustic characteristics.
A further deflecting means, for deflecting a combustion gas stream emerging from the further burner into the further inflow direction, is preferably provided in the region of the opening of the further burner.
A combustion of the combustion gas stream from the burner in an energy column and a combustion of the combustion gas stream from the further burner in a further energy column can preferably be produced, which energy columns respectively represent an extension of the combustion gas stream, with the orthogonal component and the further orthogonal component being of such a magnitude and such an orientation that the energy column from the burner and the energy column from the further burner overlap. An energy column is formed by the combustion of the combustion gas stream emerging from the burner, representing one column. Such an arrangement of mutually influencing combustions from two burners leads to a particularly efficient suppression of thermoacoustic oscillations. The overlapping energy columns have the effect that the pressure and power fluctuations which originate from these energy columns and may be the cause of a combustion oscillation also overlap. This overlapping achieves the effect of reducing or suppressing a combustion oscillation.
The deflecting means is preferably a wall protruding into the combustion chamber and surrounding the opening. It is further preferred for the deflecting means to have a breakaway edge for swirls, which can be induced by the combustion gas stream. Such a breakaway edge for swirls has the effect of producing swirls in the combustion gas stream at the deflecting means. These swirls lead to the formation at the deflecting means of a return flow area for the combustion gas stream, in which a location for the combustion is stabilized. Such stabilization allows acoustic detuning of the system to be controlled better. Moreover, fuel and combustion air are mixed still further by the swirling, which favorably also has the additional advantage that NOx emission is reduced.
The deflecting means is preferably a hollow cylinder or a hollow truncated cone with covering surfaces sloping with respect to each other. These covering surfaces are imaginary surfaces, that is to say not surfaces made solidly of a material. They are formed by the edge of the lateral surface of the hollow cylinder or hollow truncated cone. One covering surface is thus the imaginary connecting surface of the edge facing the opening and the other covering surface is the imaginary connecting surface of the edge protruding into the combustion chamber. This is a particularly simple and effective design of the deflecting means.
The combustion chamber is preferably an annular combustion chamber, especially for a gas turbine. The annular combustion chamber has a complex geometry. In such a system, the occurrence of thermoacoustic oscillations is not predictable and is especially difficult to control. Deflecting means allow even such a system to be acoustically detuned by simple design measures with the result of suppressing thermoacoustic oscillations. The annular combustion chamber preferably has a multiplicity of burners, a deflecting means being arranged in each case in the region of a respective opening for the majority of these burners, in particular for all the burners.